It has been recognized in the radiopharmaceutical arts that technetium-99m sulfur colloid radiopharmaceuticals having a particle size distribution within certain ranges are useful diagnostic tools in reticuloendothelial imaging, particularly of the liver and spleen. Such radiopharmaceuticals and reagent kits for their preparation are commercially available. However, each of these commercial preparations is disadvantageous in one or more particulars.
Reagent kits commercially available for the preparation of Tc-99m sulfur colloid radiopharmaceuticals can be considered disadvantageous in that multiple manipulative steps are required to form the technetium-99m colloid. In each instance the mixing together of more than one reagent is required prior to labeling the colloid with technetium-99m. Additionally, incubation in a heating water bath is often required to effect complete labeling. The need for such manipulations is both time consuming and inconvenient to the practitioner as well as increasing the potential radiation exposure to the operator. A reagent kit with more than one vial is costly in terms of materials, handling and packaging.
Another feature of the sulfur colloid preparations commercially available which could be considered disadvantageous is that, once they are labeled with technetium-99m, their in vitro stability is limited to about 6 hours. After this time, there is the possibility that a flocculent precipitate could form as a result of agglomeration of the individual colloidal particles. Such agglomerates are disadvantageous in that they become entrapped in the pulmonary capillary bed following intravenous injection and thus prevent the Tc-99m from efficiently reaching the liver or spleen to carry out the desired scan. The presence of stabilizing agents in the commercial sulfur colloid preparations has been seemingly ineffectual in extending the in vitro stability of the radiopharmaceutical prepared therefrom beyond 6 hours.
In accordance with the present invention, the above disadvantageous features of presently available commercial preparations have been eliminated.